The parent company of Boots is investing up to $1.3 billion in an American pharmaceuticals distributor in a big step towards the chemist fulfilling its ambition of cracking the US market.

Alliance Boots and its American retail partner, Walgreens, are each taking stakes of up to 11.5 per cent in AmerisourceBergen, a Pennsylvania-based company, in a gradual investment over five years.

The deal comes days after Stefano Pessina, the Italian billionaire who co-owns Alliance Boots, said that he was keen to forge more international alliances. “My satisfaction is in putting together many, many different companies over many years,” he said